Configuring Link-State Tracking

Finding Feature
Information

Your software release may not support all the features documented in
this module. For the latest caveats and feature information, see Bug Search
Tool and the release notes for your platform and software release. To find
information about the features documented in this module, and to see a list of
the releases in which each feature is supported, see the feature information
table at the end of this module.

Use Cisco Feature Navigator to find information about platform support
and Cisco software image support. To access Cisco Feature Navigator, go to
http:/​/​www.cisco.com/​go/​cfn. An account on Cisco.com is
not required.

Restrictions for Configuring Link-State Tracking

You can configure only two link-state groups per switch.

An interface cannot be a member of more than one link-state group.

An interface that is defined as an upstream interface in a link-state group cannot also be defined as a downstream interface in the link-state group.

Do not enable link-state tracking on individual interfaces that will part of a downstream EtherChannel interface.

Understanding
Link-State Tracking

Link-state tracking,
also known as trunk failover, binds the link state of multiple interfaces.
Link-state tracking can be with server NIC adapter teaming to provide
redundancy in the network. When the server NIC adapters are configured in a
primary or secondary relationship, and the link is lost on the primary
interface, network connectivity is transparently changed to the secondary
interface.

Note

An interface can be an aggregation of ports (an EtherChannel) or a
single physical port in either access or trunk mode .

The configuration in
this figure ensures that the network traffic flow is balanced.

Figure 1. Typical
Link-State Tracking Configuration

For links to
switches and other network devices

Server 1 and
server 2 use switch A for primary links and switch B for secondary links.

Server 3 and
server 4 use switch B for primary links and switch A for secondary links.

Link-state group 1
on switch A

Switch A
provides primary links to server 1 and server 2 through link-state group 1.
Port 1 is connected to server 1, and port 2 is connected to server 2. Port 1
and port 2 are the downstream interfaces in link-state group 1.

Port 5 and
port 6 are connected to distribution switch 1 through link-state group 1. Port
5 and port 6 are the upstream interfaces in link-state group 1.

Link-state group 2
on switch A

Switch A
provides secondary links to server 3 and server 4 through link-state group 2.
Port 3 is connected to server 3, and port 4 is connected to server 4. Port 3
and port 4 are the downstream interfaces in link-state group 2.

Port 7 and
port 8 are connected to distribution switch 2 through link-state group 2. Port
7 and port 8 are the upstream interfaces in link-state group 2.

Link-state group 2
on switch B

Switch B
provides primary links to server 3 and server 4 through link-state group 2.
Port 3 is connected to server 3, and port 4 is connected to server 4. Port 3
and port 4 are the downstream interfaces in link-state group 2.

Port 5 and
port 6 are connected to distribution switch 2 through link-state group 2. Port
5 and port 6 are the upstream interfaces in link-state group 2.

Link-state group 1
on switch B

Switch B
provides secondary links to server 1 and server 2 through link-state group 1.
Port 1 is connected to server 1, and port 2 is connected to server 2. Port 1
and port 2 are the downstream interfaces in link-state group 1.

Port 7 and
port 8 are connected to distribution switch 1 through link-state group 1. Port
7 and port 8 are the upstream interfaces in link-state group 1.

In a link-state group,
the upstream ports can become unavailable or lose connectivity because the
distribution switch or router fails, the cables are disconnected, or the link
is lost. These are the interactions between the downstream and upstream
interfaces when link-state tracking is enabled:

If any of the
upstream interfaces are in the link-up state, the downstream interfaces can
change to or remain in the link-up state.

If all of the
upstream interfaces become unavailable, link-state tracking automatically puts
the downstream interfaces in the error-disabled state. Connectivity to and from
the servers is automatically changed from the primary server interface to the
secondary server interface. For example, in the previous figure, if the
upstream link for port 6 is lost, the link states of downstream ports 1 and 2
do not change. However, if the link for upstream port 5 is also lost, the link
state of the downstream ports changes to the link-down state. Connectivity to
server 1 and server 2 is then changed from link-state group1 to link-state
group 2. The downstream ports 3 and 4 do not change state because they are in
link-group 2.

If the link-state
group is configured, link-state tracking is disabled, and the upstream
interfaces lose connectivity, the link states of the downstream interfaces
remain unchanged. The server does not recognize that upstream connectivity has
been lost and does not failover to the secondary interface.

You can recover a
downstream interface link-down condition by removing the failed downstream port
from the link-state group. To recover multiple downstream interfaces, disable
the link-state group.

Technical
Assistance

Description

Link

The Cisco
Support website provides extensive online resources, including documentation
and tools for troubleshooting and resolving technical issues with Cisco
products and technologies.

To receive
security and technical information about your products, you can subscribe to
various services, such as the Product Alert Tool (accessed from Field Notices),
the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS)
Feeds.

Access to
most tools on the Cisco Support website requires a Cisco.com user ID and
password.